Component reachable expandable heat plate

ABSTRACT

Some embodiments of the invention provide a heat plate system that includes a closed vessel having at least one flexible surface. The flexible surface allows the vessel to come into intimate contact with heat-generating components (e.g., integrated circuits) residing at varying heights above the floor of a module (e.g., an avionics module). In some embodiments, the material may allow the heat plate to expand in response to absorbing heat, so that it may mold itself around the contours of different heat-generating components, increasing the surface area contact between the heat plate and the components, and increasing the heat plate&#39;s ability to conduct heat away from the components.

FIELD OF INVENTION

This invention deals generally with heat transfer, and more particularlywith heat plates and/or heat pipes used in transferring heat away fromone or more heat-generating components.

BACKGROUND

Proper thermal management is critical to the successful operation ofmany types of devices. In this respect, modern jet aircraft includenumerous types of devices which generate significant heat duringoperation, including avionic electronics, radar and directed-energysystems. As an example, avionics components commonly use integratedcircuits (hereinafter called “chips” for convenience) for computingapplications which can generate significant heat during operation.

Various techniques are known for transferring heat away from devicesand/or their components during operation, to keep the devicesfunctioning properly. For example, heat plates are commonly used totransfer heat away from the tops of the chip(s) in an avionics moduletoward the module's edge (e.g. to one or more side walls). Often athermal interface transfers heat from the edge to a chassis, which isoften a cooled component in which the module resides.

Heat plates commonly employ heat pipe technology. A heat pipe is aclosed vessel which stores fluid in two states, or phases (i.e., liquidand gas), and which makes use of changes between the states to transferheat. In some heat pipes, a volume of liquid is stored in the heat pipeat a given temperature, and then a vacuum is imposed in the vessel. Thevessel is then sealed, so that the pressure level within the vesselcauses some of the liquid to change to a gaseous state. The two-phasesystem inside the vessel remains at equilibrium, meaning that theboiling point and condensation point of the fluid in the vessel are atapproximately the system's temperature. If heat is then absorbed at aparticular location on the vessel, the heat causes liquid stored at thatlocation to boil and be converted to gas, the heat being transferred tothe gas, and pressure in the system increasing. A pressure increasecauses the condensation point to increase as well, so that condensationbegins occurring almost immediately at a different location in the heatpipe, typically where it is coolest, so that heat is transferred fromthe gas within the vessel to the external environment near the coollocation. The liquid which results from this condensation transfers fromthe cool location back to the heated region (e.g., via a wick, one ormore micro-grooves, and/or other mechanism(s)) so that theevaporation-and-condensation cycle can begin again.

Within a heat pipe, heat is transferred at approximately sonic speedfrom a heated location to a cooled location. As such, if a heat pipe islong enough to transfer heat a sufficient distance away from a heatedlocation of a component, the heat pipe can effectively cool thecomponent, without the need for any auxiliary pumping or moving parts.

FIG. 1 depicts the operation of an example conventional heat pipe 100.In this example, water is the fluid within the closed vessel that isused to transfer heat, although any of numerous materials couldalternatively be used. In the example of FIG. 1, evaporator region 105is heated, such as by a component (e.g., a chip, not shown in FIG. 1)which generates heat during operation. This heat causes water nearevaporator region 105 to be turned to vapor. The heat transfers throughthe vapor to condenser region 110, which is a cooled location in heatpipe 100. Heat is then transferred to the external environment, causingthe water at to be converted back to liquid, and this liquid istransferred by wick 115 (e.g., via capillary action) to evaporatorregion 105.

SUMMARY

The inventors have appreciated that employing heat plates to cool thenumerous types of devices and components used in modern applications canpresent challenges. Components on modern jet aircraft serve as anillustrative example. On a modern jet aircraft, there may be dozens ofdifferent avionics modules, each having chips disposed at differentlocations within the module. In modules in which chips are attached tothe module floor, different chips may be at different heights. Toprovide proper thermal management for all types of modules, a differentheat plate may need to be separately configured to properly accommodatethe location and height of the chips therein. In this respect, a heatplate is generally designed to come into intimate contact with the chipsin a module so as to effectively transfer heat away, without applying somuch pressure that any chip's operation is affected. As such, preparinga heat plate for use with a module usually involves configuring theplate to reach each of its chips at a particular height with greatspecificity. This is difficult to accomplish using conventionalfabrication techniques.

One conventional approach to overcoming these difficulties is to employa conformable, compressible thermal interface layer between each chipand the heat plate. In this approach, a thermal interface typically sitsatop each chip, and contacts the heat plate when the heat plate islowered into the module in which the chip resides. Because the thermalinterface is conformable, the heat plate need not be configured toaccommodate varying chip heights with great specificity. However,thermal interfaces are notoriously poor at conducting heat away from achip, because they are typically made from materials which are highlyconformable but not very thermally conductive. For example, many thermalinterfaces cause about a 50% loss in thermal conductivity when comparedwith direct contact between a chip and a heat plate.

The inventors have recognized that other conformable materials which aremore thermally conductive could be used in a thermal interface layer.For example, silver or copper pastes are both conformable and thermallyconductive. However, the use of pastes can make module assemblyproblematic, because applying a paste on a set of chips having varyingheights so that the paste atop each chip reaches the same height can bedifficult. In addition, pastes are messy, and can therefore make modulemaintenance difficult.

In contrast to conventional approaches, some embodiments of theinvention provide a heat plate system which includes a closed vesselhaving at least one flexible surface. The flexible surface allows thevessel to come into intimate contact with heat-generating components ofvarying heights. In some embodiments, the heat plate may be expandableduring use (e.g., in response to being heated). As such, the heat platemay mold itself around the contours of different heat-generatingcomponents, increasing the surface area contact between the heat plateand the components, and increasing the heat plate's ability to conductheat away from the components. In some embodiments of the invention, aheat plate may interface directly with one or more of the module's sidewalls, and/or a cooling mechanism. As a result, heat is transferred tothe external environment via the module's periphery rather than throughits cover, which may provide greater control and effectiveness withrespect to thermal management than conventional approaches allow.

The foregoing is a non-limiting summary of the invention, someembodiments of which are defined by the attached claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 is a symbolic representation of the operation of a conventionalheat pipe or heat plate, according to the prior art;

FIG. 2 is a perspective view of a heat plate, implemented in accordancewith some embodiments of the invention, for use with an example module;

FIG. 3 is a side view showing a heat plate, implemented in accordancewith some embodiments of the invention, installed in a module; and

FIG. 4 is a side view of a heat plate, implemented in accordance withsome embodiments of the invention, illustrating the heat plate'sflexibility and expandability.

DETAILED DESCRIPTION

Some embodiments of the invention provide a heat plate system whichincludes a closed vessel having at least one surface that is pliableand/or flexible, allowing the vessel to come into close contact withcontoured surfaces of heat-generating components of varying heights, andenabling effective heat transfer away from those components. In someembodiments of the invention, a heat plate may be expandable, such asupon the absorption of heat, so as to increase the component surfacearea with which the heat plate system comes into contact, and therebyimproving thermal conductivity. In addition, some embodiments of theinvention may provide a heat plate system for use with heat-generatingcomponents residing in a module housing which is designed to conductheat to the housing's peripheral walls and/or a cooling mechanism,rather than to the housing's cover, to provide greater control andeffectiveness with respect to heat transfer than conventional systemsprovide.

FIG. 2 depicts an example heat plate system 205 that is designed for usewith module 220. Module 220 includes components which generate heatduring operation, and may be an avionics module, or any other suitabletype of module. In the example shown in FIG. 2, module 220 includes fourheat-generating components, namely integrated circuits 210A, 210B, 210Cand 210D. It should be appreciated, however, that embodiments of theinvention may be employed with modules having any suitable number ofheat-generating components, which may or may not include integratedcircuits.

In module 220, components 210A-210D reside on module floor 225. Itshould be appreciated, however, that embodiments of the invention arenot limited to being used with components residing on the floor of amodule, and may be used with components in any suitable location. Forexample, components may be elevated above a module floor, reside withina recess within a module's floor, be attached to one or more of themodule's side walls, and/or reside in any other suitable location(s).

In module 220, periphery walls 215 define a cavity in which components210A-210D reside. As explained further below, in some embodiments of theinvention, one or more of walls 215 may contact, or otherwise bethermally coupled to, one or more external cooling components. Forexample, one or more of walls 215 may contact components through or overwhich cooling fluid (which may comprise any suitable gas and/or liquid)flows. It should be appreciated, however, that embodiments of theinvention are not limited to being used in conjunction with moduleshaving walls which contact external cooling components.

Arrow 230 in FIG. 2 indicates that example heat plate 205 is designed tobe introduced into the cavity defined by walls 215 from above. However,it should be appreciated that the invention is not limited to beingimplemented in this manner, and that heat plate 205 may be introduced into or on to a module in any suitable manner. For example, heat plate 205may be injected, fed or introduced into a cavity in any other suitableway.

FIG. 3 is a side view (specifically, viewed along line 301 in FIG. 2)which shows heat plate 205 having been introduced into the cavitydefined by walls 215. In the example shown in FIG. 3, the dimensions ofheat plate 205 approximate those of the cavity into which it isintroduced, such that it contacts walls 215 when in use. However, itshould be appreciated that the invention is not limited to such animplementation, and that a heat plate may take any suitable shape, whichmay or may not coincide with the shape of a cavity into which it isintroduced. As one example, heat plate 205 could alternatively bedesigned to come into contact with one or more of side walls 215 (e.g.,one or more walls in contact with a cooling element) but not all of theside walls.

In the example shown in FIG. 3, bottom surface 315 of heat plate 205comes into contact with the top surfaces 310B, 310C of components 210B,210C, respectively, when introduced, although component 210B is tallerthan component 210C. In this respect, in some embodiments of theinvention, heat plate 205 is at least partially formed of a flexible,pliable material which allows bottom surface 315 to come into intimatecontact with components of varying heights. Any of numerous materialsmay be used. In some embodiments, it may be desirable to employ amaterial or materials which exhibit sufficient flexibility to allow theheat plate to come into intimate contact with components at varyingheights within a module, a tensile strength and/or tensile modulus thatis sufficient to allow for stretching with minimal risk of ruptureduring operation, and good heat transfer capability. Materials havingsuitable physical properties include Kapton® polyimide film (whichexhibits a tensile strength of approximately 231 Mpa and Young's modulusof approximately 2.5 GPa at room temperature), aluminum foil (whichexhibits a tensile strength of 330 Mpa and Young's modulus of 70 GPa atroom temperature), and gold foil (which exhibits a tensile strength of330 Mpa and Young's modulus of 120 MPa at room temperature), althoughthe inventors have recognized that in certain applications it may beadvantageous to employ materials having dielectric or non-conductiveproperties so that the surface of the heat plate which contactselectrical components (e.g., circuits) does not interfere with theiroperation. Thus, in certain applications, Kapton® polyimide film mayexhibit more suitable physical properties than aluminum or gold foil. Amoisture barrier layer (not shown in FIG. 3), which may be formed of,for example, rubber, flexible glass, and/or any other suitablematerial(s)), may be used to prevent vapor from transmitting through thebottom surface of the heat plate if Kapton® polyimide film is used.

In the example shown in FIG. 3, heat plate 205 conducts heat from thetop surfaces 310B and 310C of components 210B and 210C, respectively, tocooled regions 305 which contact walls 215. More specifically, fluidwithin heat plate 205 proximate top surfaces 310B and 310C is heated andconverts to a vapor state, and the heat transfers through the vapor tocooled regions 305 and then through walls 215 to the externalenvironment. The fluid then converts back to a liquid state, and istransferred back to locations proximate top surfaces 310B and 310C(e.g., by a wick, not shown), so that it may transfer additional heatgenerated by components 210B and 210C away from the components.

In some embodiments, the material(s) from which heat plate 205 is formedmay allow it to expand as it absorbs heat generated by modulecomponents, so that as heat is generated, bottom surface 315 is forcedinto more intimate contact with the components, increasing the surfacearea of heat plate 205 across which heat may be conducted. FIG. 4illustrates this capability. In FIG. 4, heated generated by component210A causes heat plate 205 to expand, forcing regions 415 and 420 ofheat plate 205 to bend along the edges of component 210, in contrast toFIG. 3, in which a lack of heat generated by component 210 leavesregions 315 and 320 of heat plate 205 largely undeformed. By expandingwhen heat is absorbed, heat plate 205 forces regions into intimatecontact with heat-generating components and provides an efficient heattransfer mechanism.

Heat plate 205 may employ any of numerous types of fluids to performheat transfer. The inventors have observed that fluids which transitionwithout difficulty between liquid and vapor phases, and which expandwhen entering the vapor phase, may prove advantageous in certainapplications. Examples of fluids exhibiting these characteristicsinclude water, alcohol and paraffin. However, it should be appreciatedthat any suitable fluid(s) may be used, as embodiments of the inventionare not limited in this respect.

It should also be appreciated that numerous advantages may flow from theexample arrangements shown in FIGS. 2-4. For example, a heat plateformed of one or more materials that enable the heat plate to expand asheat is absorbed enables the heat plate to expand to a volume at whichheat transfer may be more effectively performed than in conventionalarrangements. In addition, a heat plate designed to transfer heat to oneor more side walls of a module, where cooling components may be located,may provide a more effective mechanism than conventional arrangementswhich rely on transfer or heat to the module's cover.

It should further be appreciated that the implementation examplesdescribed above are intended to be illustrative rather than limiting,and that numerous variations on these examples are possible. Forexample, embodiments of the invention may be used to transfer heat awayfrom any suitable component(s), which may or may not include anintegrated circuit. In addition, embodiments of the invention may beused in conjunction with any suitable collection of components, whichmay or may not include or comprise a functional module such as anavionics module. The collection of components may be of any suitablesize and include any suitable quantity of components. Embodiments of theinvention are not limited in this respect.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art. Such alterations, modifications, and improvements are intendedto be part of this disclosure, and are intended to be within the spiritand scope of the invention. Accordingly, the foregoing description anddrawings are by way of example only.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in this application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Use of ordinal terms such as “first,” “second,” “third,” etc. in theclaims to modify a claim element does not by itself connote anypriority, precedence or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claimed element having a certainname from another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is used for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having,” “containing,” “involving,”and variations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. An apparatus for use with a module comprisingcomponents which generate heat during operation, each of the componentshaving a component surface, the apparatus comprising: a closed vesseladapted for installation within the module to conduct heat away from thecomponents, the closed vessel storing a fluid in a liquid state and agaseous state, the vessel comprising at least one vessel surface adaptedto contact the component surface of each component, the at least onevessel surface being at least partially formed of a material exhibitinga Young's modulus of at least 120 MPa and a tensile strength of at least231 MPa at room temperature.
 2. The apparatus of claim 1, wherein thematerial exhibits a Young's modulus of approximately 2.5 GPa at roomtemperature.
 3. The apparatus of claim 2, wherein the material is apolyimide film.
 4. The apparatus of claim 1, wherein the material isnon-conductive or dielectric.
 5. The apparatus of claim 1, wherein thematerial exhibits a tensile strength of approximately 330 MPa at roomtemperature.
 6. The apparatus of claim 5, wherein the material comprisesat least one of an aluminum foil and a gold foil.
 7. The apparatus ofclaim 1, wherein the component surface of each of the components residesat a different height above a floor of the module, and wherein thevessel surface comes into contact with substantially the entirety ofeach component surface when installed in the module.
 8. The apparatus ofclaim 1, wherein the material accommodates expansion of the fluid inresponse to absorbing heat generated by the plurality of components. 9.The apparatus of claim 1, wherein the module comprises side wallsextending orthogonally from a floor of the module, and wherein theclosed vessel is adapted to conduct heat generated by the components toat least one of the side walls.
 10. The apparatus of claim 1, whereinthe fluid comprises one or more of water, alcohol and paraffin.
 11. Theapparatus of claim 1, in combination with the module.
 12. The apparatusof claim 1, wherein the module is an avionics module.
 13. The apparatusof claim 1, wherein the plurality of components comprise at least oneintegrated circuit.
 14. A method for use in a system comprising a modulehaving components which generate heat during operation, each of thecomponents having a component surface, the method comprising an act of:(A) employing a closed vessel to conduct heat away from the components,the vessel being adapted for installation within the module and storinga fluid in a liquid state and a gaseous state, the vessel comprising atleast one vessel surface adapted to contact the component surface ofeach component, the at least one vessel surface being at least partiallyformed of a material exhibiting a Young's modulus of at least 120 MPaand a tensile strength of at least 231 MPa at room temperature.
 15. Themethod of claim 14, wherein the material exhibits a Young's modulus ofapproximately 2.5 GPa at room temperature.
 16. The method of claim 15,wherein the material is a polyimide film.
 17. The method of claim 14,wherein the material is non-conductive or dielectric.
 18. The method ofclaim 14, wherein the component surface of each of the componentsresides at a different height above a floor of the module, and whereinthe act (A) comprises causing the vessel surface to come into contactwith substantially the entirety of each component surface.
 19. Themethod of claim 14, wherein the module comprises side walls extendingorthogonally from a floor of the module, and wherein the act (A)comprises conducting heat generated by the components to at least one ofthe side walls.
 20. The method of claim 14, wherein the plurality ofcomponents comprise at least one integrated circuit.